The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
A typical dual clutch transmission configuration includes a pair of mutually exclusively operating input clutches which drive a pair of input shafts. The input shafts may be disposed on opposite sides of an output shaft or may be disposed concentrically between spaced-apart output shafts. One of each of a plurality of pairs of constantly meshing gears is freely rotatably disposed on one of the shafts and the other of each pair of gears is coupled to one of the other shafts. A plurality of synchronizer clutches selectively couple the freely rotatable gears to the associated shaft to achieve forward and reverse gear ratios. After the synchronizer clutch is engaged, the input clutch associated with the input shaft having the engaged synchronizer clutch is applied to transmit power through the transmission. Reverse gear is similarly achieved through an additional (idler) gear to provide torque reversal.
Dual clutch transmissions are known for their sporty, performance oriented operating characteristics which mimic those of a conventional mechanical (manual) transmission. They also typically exhibit good fuel economy due to their good gear mesh efficiency, ratio selection flexibility, reduced clutch losses and the lack of a torque converter.
There are several design considerations unique to dual clutch transmissions. For example, because of heat generated during clutch slip, the input clutches must be of relatively large size. Furthermore, such heat generation typically requires correspondingly larger and more complex cooling components capable of dissipating relatively large quantities of heat.
Cooling of the input clutches is typically achieved by a hydraulic control system having a cooling subsystem that delivers cooled hydraulic fluid to the input clutches. Such a system, itself under the control of an electronic transmission control module (TCM), includes hydraulic valves and actuators which engage the synchronizers and gear clutches.
Accordingly, there is room in the art for an apparatus and method for selectively providing cooled hydraulic fluid to the input clutches of a DCT to improve gear shift smoothness, timing, efficiency and durability while optimizing operating efficiency and thus fuel efficiency by designing such hydraulic control systems to more precisely deliver cooled hydraulic fluid to the input clutch generating the most heat.